java常用代码

1、List遍历

List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
items.add("E");

//lambda
//Output : A,B,C,D,E
items.forEach(item->System.out.println(item));
    
//Output : C
items.forEach(item->{
    if("C".equals(item)){
        System.out.println(item);
    }
});
    
//method reference
//Output : A,B,C,D,E
items.forEach(System.out::println);

//Stream and filter
//Output : B
items.stream()
    .filter(s->s.contains("B"))
    .forEach(System.out::println);

2、Map遍历

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);

items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));

items.forEach((k,v)->{
    System.out.println("Item : " + k + " Count : " + v);
    if("E".equals(k)){
        System.out.println("Hello E");
    }
});

 3、遍历enum

public enum ColumnTypeEnums {
    INTEGER("int", "Integer"),
    VARCHAR("varchar", "String"),
    DATE("date", "java.util.Date"),
    TIME("datetime", "java.util.Date"),

    NUMERIC("numeric", "java.math.BigDecimal"),
    DECIMAL("decimal", "java.math.BigDecimal"),
    TINYINT("tinyint", "byte"),
    SMALLINT("smallint", "short"),
    BIGINT("bigint", "long"),
    FLOAT("float", "double"),
    DOUBLE("double", "double"),
    CHAR("char", "String");

    private String pdm;
    private String java;

    public void setPdm(String pdm) {
        this.pdm = pdm;
    }

    public void setJava(String java) {
        this.java = java;
    }

    public static ColumnTypeEnums getByPdm(String pdm) {
        ColumnTypeEnums e = null;
        for (ColumnTypeEnums en : ColumnTypeEnums.values()) {
            if (en.getPdm().equals(pdm)) {
                e = en;
            }
        }
        return e;
    }

    public static void main(String[] args) {
        ColumnTypeEnums e = ColumnTypeEnums.getByPdm("tinyint");
        Console.log("===============");
        Console.log("{},{},{}", e.name(), e.getPdm(), e.getJava());
    }
}