Java String Comparison: equals()? ==?

It's a issue of Java programming language, not Android.

String in Java is object, of java.lang.String class. It have some ways to be initialized, such as:
String s = "hello";
String s = new String("hello");
Is it same?

Java's String class provide a method equals() to compare two string. Sometimes we can use "==", but not always! Here are some examples:

package com.exercise.AndroidStringCompare;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class AndroidStringCompare extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       TextView Result1 = (TextView)findViewById(R.id.result1);
       TextView Result2 = (TextView)findViewById(R.id.result2);
       TextView Result3 = (TextView)findViewById(R.id.result3);
       TextView Result4 = (TextView)findViewById(R.id.result4);
       TextView Result5 = (TextView)findViewById(R.id.result5);
       TextView Result6 = (TextView)findViewById(R.id.result6);
       TextView Result7 = (TextView)findViewById(R.id.result7);
       TextView Result8 = (TextView)findViewById(R.id.result8);
       TextView Result9 = (TextView)findViewById(R.id.result9);
       TextView Result10 = (TextView)findViewById(R.id.result10);
      
       String s1 = "hello";
       String s2 = "hello";
       String s3 = s1;
       String s4 = "h" + "e" + "l" + "l" + "o";
       String s5 = new String("hello");
       String s6 = new String(new char[]{'h', 'e', 'l', 'l', 'o'});
      
      
       Result1.setText(s1 + " == " + s2 + ": " + (s1 == s2));
       Result2.setText(s1 + " equals " + s2 + ": " + (s1.equals(s2)));
       Result3.setText(s1 + " == " + s3 + ": " + (s1 == s3));
       Result4.setText(s1 + " equals " + s3 + ": " + (s1.equals(s3)));
       Result5.setText(s1 + " == " + s4 + ": " + (s1 == s4));
       Result6.setText(s1 + " equals " + s4 + ": " + (s1.equals(s4)));
       Result7.setText(s1 + " == " + s5 + ": " + (s1 == s5));
       Result8.setText(s1 + " equals " + s5 + ": " + (s1.equals(s5)));
       Result9.setText(s1 + " == " + s6 + ": " + (s1 == s6));
       Result10.setText(s1 + " equals " + s6 + ": " + (s1.equals(s6)));
   }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   >
<TextView 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="@string/hello"
   />
<TextView 
   android:id="@+id/result1"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result2"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result3"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result4"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result5"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result6"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result7"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result8"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result9"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
<TextView 
   android:id="@+id/result10"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
</LinearLayout>